A fart that results in you shitting yourself. It feels like it is going to be a normal fart but when you go to release the fart it is not just gaseous but also comes with out with liquid feces. The liquid feces is the sneaky part because it uses the fart as means to make you shit yourself.

I had a sneaky fart today when I was waiting for the bus so i had to run home to change my underwear.